Ubuntu Security Notice USN-3918-3

Ubuntu Security Notice 3918-3 - USN-3918-1 fixed vulnerabilities in Firefox. The update caused web compatibility issues with some websites. This update fixes the problem. Multiple security issues were discovered in Firefox. If a user were tricked in to opening a specially crafted website, an attacker could potentially exploit these to cause a denial of service via application crash, denial of service via successive FTP authorization prompts or modal alerts, trick the user with confusing permission request prompts, obtain sensitive information, conduct social engineering attacks, or execute arbitrary code. A mechanism was discovered that removes some bounds checking for string, array, or typed array accesses if Spectre mitigations have been disabled. If a user were tricked in to opening a specially crafted website with Spectre mitigations disabled, an attacker could potentially exploit this to cause a denial of service, or execute arbitrary code. It was discovered that Upgrade-Insecure-Requests was incorrectly enforced for same-origin navigation. An attacker could potentially exploit this to conduct man-in-the-middle attacks. Various other issues were also addressed.

A mechanism was discovered that removes some bounds checking for string, array, or typed array accesses if Spectre mitigations have been disabled. If a user were tricked in to opening a specially crafted website with Spectre mitigations disabled, an attacker could potentially exploit this to cause a denial of service, or execute arbitrary code. (CVE-2019-9793)

It was discovered that Upgrade-Insecure-Requests was incorrectly enforced for same-origin navigation. An attacker could potentially exploit this to conduct man-in-the-middle (MITM) attacks. (CVE-2019-9803)

Update instructions:

The problem can be corrected by updating your system to the followingpackage versions:

Ubuntu 18.10: firefox 66.0.2+build1-0ubuntu0.18.10.1

Ubuntu 18.04 LTS: firefox 66.0.2+build1-0ubuntu0.18.04.1

Ubuntu 16.04 LTS: firefox 66.0.2+build1-0ubuntu0.16.04.1

Ubuntu 14.04 LTS: firefox 66.0.2+build1-0ubuntu0.14.04.1

After a standard system update you need to restart Firefox to makeall the necessary changes.